hydromancy

/ˈhaɪdrəˌmænsi/
noun
  1. Divination or fortune-telling by interpreting the appearance, movement, or sounds of water.
    • In ancient Greece, hydromancy was practiced by observing the patterns of water in a bowl.
    • The wizard's hydromancy revealed a vision of a coming flood in the crystal-clear pool.
    • Some cultures used hydromancy to predict rainfall or the outcome of battles.